Suspension noise and sagging

There is a bad rattle from I guess the stabilizer arm that has nothing but a long bolt with a nut holding it on with about two inches of play in it (both driver and passenger side), and the driver side suspension is slightly lower than the other side. I know something is not right but I just cannot put my finger on what is causing the sag, it looks like everything is worn and cracked! But both sides look equally worn out, so whati s causing the sag?

Also, I use my truck for hauling a lot of scrap metal and I was thinking of adding a couple more leaf springs so that it can handle the weight better. I do my own mechanic work cause I do not trust other "mechanics" and I always know exactly what has been done. The truck was my best friend's and he passed away and left it to me, so it really means a lot. So I want to make sure I get it right being I do not know a lot about suspension and exactly what makes it preform at its best. If someone has time to break it down to me, I would love to learn. Thank you